In-vehicle battery monitor

ABSTRACT

An apparatus and a method of monitoring a battery in an automotive vehicle are provided. An output is provided which can be a relative output as a function of minimum and maximum parameters of the battery.

The present application is a Continuation-In-Part of and claims priorityof U.S. patent application Ser. No. 09/960,117, filed Sep. 20, 2001,which is a Continuation-In-Part of Ser. No. 09/564,740, filed May 4,2000, now U.S. Pat. No. 6,331,762, which is a Continuation-In-Part ofapplication Ser. No. 08/962,754, filed Nov. 3, 1997, now U.S. Pat. No.6,081,098 and also a Continuation-In-Part of application Ser. No.09/575,627, filed May 22, 2000, which is a Continuation-In-Part ofapplication Ser. No. 08/962,754, filed Nov. 3, 1997, now U.S. Pat. No.6,081,098 and also claims priority to Provisional Application Ser. No.60/132,622, filed May 5, 1999, and entitled AUTOMOTIVE VEHICLE BATTERYCHARGING SYSTEM; U.S. Provisional Application No. 60/165,208, filed Nov.12, 1999, and entitled ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE;and Provisional Application Ser. No. 60/175,762, filed Jan. 12, 2000,and entitled ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE, thisapplication is also a Continuation-In-Part of Ser. No. 10/046,659, filedOct. 29, 2001, which is a Divisional of Ser. No. 09/564,740, filed May4, 2000, now U.S. Pat. No. 6,331,762, and also claims priority toProvisional Application Ser. No. 60/132,622, filed May 5, 1999, andentitled AUTOMOTIVE VEHICLE BATTERY CHARGING SYSTEM; U.S. ProvisionalApplication No. 60/165,208, filed Nov. 12, 1999, and entitled ENERGYMANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE; and Provisional ApplicationSer. No. 60/175,762, filed Jan. 12, 2000, and entitled ENERGY MANAGEMENTSYSTEM FOR AUTOMOTIVE VEHICLE which are incorporated herein by referencein their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to vehicles. More specifically, thepresent invention relates to battery monitors used to monitor batteriesused in vehicles. Vehicles, both automotive and electric, typicallyinclude a storage battery. For example, automotive vehicles powered bycombustion engines typically include a battery. The battery is used topower the electrical system when the engine is not running.Additionally, the engine is used to charge the battery. The engine isalso used to power electrical components of the vehicle when the engineis running.

It has typically been difficult to monitor the condition of the storagebattery used in such vehicles. This difficulty relates to all of thevariables which are factors in determining the condition of the battery,as well as the electrical connections which are made to the batteryduring its use. Attempts have been made to characterize the operation ofa battery and use “characterization curves” to determine batterycondition. However, this technique is often quite difficult to implementbecause it is difficult to determine which particular characterizationcurve the battery may be following as well as precisely where on aparticular characterization curve a battery may lie at a given moment.

This has made it difficult for a vehicle operator to accurately and inreal time determine the condition of the vehicle's battery. For example,a battery at a particular moment may have just sufficient output tostart the engine of a vehicle but provide no outward indication to theoperator that the vehicle will not be capable of starting a second time.Further, a battery that is capable of providing sufficient power at onetemperature, may fail the next morning if the temperature drops overnight.

Some attempts have been made to monitor the condition of a battery using“coulomb counting” in which the amount of charge accepted by the batteryor removed from the battery is monitored. However, such techniques haverequired a starting point (i.e., an initial value) in order to begin anyattempt to monitor battery condition. Further, such techniques may notaccount for situations in which the battery is fully charged and anyadditional current going into the battery is simply lost as heat or asituation in which the battery charge decreases during periods onnon-use. Thus, it would be desirable to have a battery monitor which iscapable of monitoring the condition of a battery in a vehicle.

Various aspects of battering testing and related technologies have beenpioneered by Midtronics, Inc. of Willowbrook, Ill. and Dr. Keith S.Champlin as shown and described in:

-   U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin, entitled    ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 3,909,708, issued    Sep. 30, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTING    DEVICE; U.S. Pat. No. 4,816,768, issued Mar. 28, 1989, to Champlin,    entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,825,170,    issued Apr. 25, 1989, to Champlin, entitled ELECTRONIC BATTERY    TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING; U.S. Pat. No.    4,881,038, issued Nov. 14, 1989, to Champlin, entitled ELECTRONIC    BATTERY TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING TO DETERMINE    DYNAMIC CONDUCTANCE; U.S. Pat. No. 4,912,416, issued Mar. 27, 1990,    to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH    STATE-OF-CHARGE COMPENSATION; U.S. Pat. No. 5,140,269, issued Aug.    18, 1992, to Champlin, entitled ELECTRONIC TESTER FOR ASSESSING    BATTERY/CELL CAPACITY; U.S. Pat. No. 5,343,380, issued Aug. 30,    1994, entitled METHOD AND APPARATUS FOR SUPPRESSING TIME VARYING    SIGNALS IN BATTERIES UNDERGOING CHARGING OR DISCHARGING; U.S. Pat.    No. 5,572,136, issued Nov. 5, 1996, entitled ELECTRONIC BATTERY    TESTER WITH AUTOMATIC COMPENSATION FOR LOW STATE-OF-CHARGE; U.S.    Pat. No. 5,574,355, issued Nov. 12, 1996, entitled METHOD AND    APPARATUS FOR DETECTION AND CONTROL OF THERMAL RUNAWAY IN A BATTERY    UNDER CHARGE; U.S. Pat. No. 5,585,416, issued Dec. 10, 1996,    entitled APPARATUS AND METHOD FOR STEP-CHARGING BATTERIES TO    OPTIMIZE CHARGE ACCEPTANCE; U.S. Pat. No. 5,585,728, issued Dec. 17,    1996, entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION    FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,589,757, issued Dec. 31,    1996, entitled APPARATUS AND METHOD FOR STEP-CHARGING BATTERIES TO    OPTIMIZE CHARGE ACCEPTANCE; U.S. Pat. No. 5,592,093, issued Jan. 7,    1997, entitled ELECTRONIC BATTERY TESTING DEVICE LOOSE TERMINAL    CONNECTION DETECTION VIA A COMPARISON CIRCUIT; U.S. Pat. No.    5,598,098, issued Jan. 28, 1997, entitled ELECTRONIC BATTERY TESTER    WITH VERY HIGH NOISE IMMUNITY; U.S. Pat. No. 5,656,920, issued Aug.    12, 1997, entitled METHOD FOR OPTIMIZING THE CHARGING LEAD-ACID    BATTERIES AND AN INTERACTIVE CHARGER; U.S. Pat. No. 5,757,192,    issued May 26, 1998, entitled METHOD AND APPARATUS FOR DETECTING A    BAD CELL IN A STORAGE BATTERY; U.S. Pat. No. 5,821,756, issued Oct.    13, 1998, entitled ELECTRONIC BATTERY TESTER WITH TAILORED    COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,831,435,    issued Nov. 3, 1998, entitled BATTERY TESTER FOR JIS STANDARD; U.S.    Pat. No. 5,914,605, issued Jun. 22, 1999, entitled ELECTRONIC    BATTERY TESTER; U.S. Pat. No. 5,945,829, issued Aug. 31, 1999,    entitled MIDPOINT BATTERY MONITORING; U.S. Pat. No. 6,002,238,    issued Dec. 14, 1999, entitled METHOD AND APPARATUS FOR MEASURING    COMPLEX IMPEDANCE OF CELLS AND BATTERIES; U.S. Pat. No. 6,037,751,    issued Mar. 14, 2000, entitled APPARATUS FOR CHARGING BATTERIES;    U.S. Pat. No. 6,037,777, issued Mar. 14, 2000, entitled METHOD AND    APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEX    IMPEDANCE/ADMITTANCE; U.S. Pat. No. 6,051,976, issued Apr. 18, 2000,    entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Pat.    No. 6,081,098, issued Jun. 27, 2000, entitled METHOD AND APPARATUS    FOR CHARGING A BATTERY; U.S. Pat. No. 6,091,245, issued Jul. 18,    2000, entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST;    U.S. Pat. No. 6,104,167, issued Aug. 15, 2000, entitled METHOD AND    APPARATUS FOR CHARGING A BATTERY; U.S. Pat. No. 6,137,269, issued    Oct. 24, 2000, entitled METHOD AND APPARATUS FOR ELECTRONICALLY    EVALUATING THE INTERNAL TEMPERATURE OF AN ELECTROCHEMICAL CELL OR    BATTERY; U.S. Pat. No. 6,163,156, issued Dec. 19, 2000, entitled    ELECTRICAL CONNECTION FOR ELECTRONIC BATTERY TESTER; U.S. Pat. No.    6,172,483, issued Jan. 9, 2001, entitled METHOD AND APPARATUS FOR    MEASURING COMPLEX IMPEDANCE OF CELL AND BATTERIES; U.S. Pat. No.    6,172,505, issued Jan. 9, 2001, entitled ELECTRONIC BATTERY TESTER;    U.S. Pat. No. 6,222,369, issued Apr. 24, 2001, entitled METHOD AND    APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEX    IMPEDANCE/ADMITTANCE; U.S. Pat. No. 6,225,808, issued May 1, 2001,    entitled TEST COUNTER FOR ELECTRONIC BATTERY TESTER; U.S. Pat. No.    6,249,124, issued Jun. 19, 2001, entitled ELECTRONIC BATTERY TESTER    WITH INTERNAL BATTERY; U.S. Pat. No. 6,259,254, issued Jul. 10,    2001, entitled APPARATUS AND METHOD FOR CARRYING OUT DIAGNOSTIC    TESTS ON BATTERIES AND FOR RAPIDLY CHARGING BATTERIES; U.S. Pat. No.    6,262,563, issued Jul. 17, 2001, entitled METHOD AND APPARATUS FOR    MEASURING COMPLEX ADMITTANCE OF CELLS AND BATTERIES; U.S. Pat. No.    6,294,896, issued Sep. 25, 2001; entitled METHOD AND APPARATUS FOR    MEASURING COMPLEX SELF-IMMITANCE OF A GENERAL ELECTRICAL ELEMENT;    U.S. Pat. No. 6,294,897, issued Sep. 25, 2001, entitled METHOD AND    APPARATUS FOR ELECTRONICALLY EVALUATING THE INTERNAL TEMPERATURE OF    AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Pat. No. 6,304,087, issued    Oct. 16, 2001, entitled APPARATUS FOR CALIBRATING ELECTRONIC BATTERY    TESTER; U.S. Pat. No. 6,310,481, issued Oct. 30, 2001, entitled    ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,313,607, issued Nov. 6,    2001, entitled METHOD AND APPARATUS FOR EVALUATING STORED CHARGE IN    AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Pat. No. 6,313,608, issued    Nov. 6, 2001, entitled METHOD AND APPARATUS FOR CHARGING A BATTERY;    U.S. Pat. No. 6,316,914, issued Nov. 13, 2001, entitled TESTING    PARALLEL STRINGS OF STORAGE BATTERIES; U.S. Pat. No. 6,323,650,    issued Nov. 27, 2001, entitled ELECTRONIC BATTERY TESTER; U.S. Pat.    No. 6,329,793, issued Dec. 11, 2001, entitled METHOD AND APPARATUS    FOR CHARGING A BATTERY; U.S. Pat. No. 6,331,762, issued Dec. 18,    2001, entitled ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE; U.S.    Pat. No. 6,332,113, issued Dec. 18, 2001, entitled ELECTRONIC    BATTERY TESTER; U.S. Pat. No. 6,351,102, issued Feb. 26, 2002,    entitled AUTOMOTIVE BATTERY CHARGING SYSTEM TESTER; U.S. Pat. No.    6,359,441, issued Mar. 19, 2002, entitled ELECTRONIC BATTERY TESTER;    U.S. Pat. No. 6,363,303, issued Mar. 26, 2002, entitled ALTERNATOR    DIAGNOSTIC SYSTEM, U.S. Pat. No. 6,392,414, issued May 21, 2002,    entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,417,669, issued    Jul. 9, 2002, entitled SUPPRESSING INTERFERENCE IN AC MEASUREMENTS    OF CELLS, BATTERIES AND OTHER ELECTRICAL ELEMENTS; U.S. Pat. No.    6,424,158, issued Jul. 23, 2002, entitled APPARATUS AND METHOD FOR    CARRYING OUT DIAGNOSTIC TESTS ON BATTERIES AND FOR RAPIDLY CHARGING    BATTERIES; U.S. Pat. No. 6,441,585, issued Aug. 17, 2002, entitled    APPARATUS AND METHOD FOR TESTING RECHARGEABLE ENERGY STORAGE    BATTERIES; U.S. Pat. No. 6,445,158, issued Sep. 3, 2002, entitled    VEHICLE ELECTRICAL SYSTEM TESTER WITH ENCODED OUTPUT; U.S. Pat. No.    6,456,045, issued Sep. 24, 2002, entitled INTEGRATED CONDUCTANCE AND    LOAD TEST BASED ELECTRONIC BATTERY TESTER; U.S. Ser. No. 09/703,270,    filed Oct. 31, 2000, entitled ELECTRONIC BATTERY TESTER; U.S. Ser.    No. 09/780,146, filed Feb. 9, 2001, entitled STORAGE BATTERY WITH    INTEGRAL BATTERY TESTER; U.S. Ser. No. 09/816,768, filed Mar. 23,    2001, entitled MODULAR BATTERY TESTER; U.S. Ser. No. 09/756,638,    filed Jan. 8, 2001, entitled METHOD AND APPARATUS FOR DETERMINING    BATTERY PROPERTIES FROM COMPLEX IMPEDANCE/ADMITTANCE; U.S. Ser. No.    09/862,783, filed May 21, 2001, entitled METHOD AND APPARATUS FOR    TESTING CELLS AND BATTERIES EMBEDDED IN SERIES/PARALLEL SYSTEMS;    U.S. Ser. No. 09/483,623, filed Jan. 13, 2000, entitled ALTERNATOR    TESTER; U.S. Ser. No. 09/960,117, filed Sep. 20, 2001, entitled    IN-VEHICLE BATTERY MONITOR; U.S. Ser. No. 09/908,389, filed Jul. 18,    2001, entitled BATTERY CLAMP WITH INTEGRATED CIRCUIT SENSOR; U.S.    Ser. No. 09/908,278, filed Jul. 18, 2001, entitled BATTERY CLAMP    WITH EMBEDDED ENVIRONMENT SENSOR; U.S. Ser. No. 09/880,473, filed    Jun. 13, 2001; entitled BATTERY TEST MODULE; U.S. Ser. No.    09/940,684, filed Aug. 27, 2001, entitled METHOD AND APPARATUS FOR    EVALUATING STORED CHARGE IN AN ELECTROCHEMICAL CELL OR BATTERY; U.S.    Ser. No. 09/977,049, filed Oct. 12, 2001, entitled PROGRAMMABLE    CURRENT EXCITER FOR MEASURING AC IMMITTANCE OF CELLS AND BATTERIES;    U.S. Ser. No. 60/330,441, filed Oct. 17, 2001, entitled ELECTRONIC    BATTERY TESTER WITH RELATIVE TEST OUTPUT; U.S. Ser. No. 60/348,479,    filed Oct. 29, 2001, entitled CONCEPT FOR TESTING HIGH POWER VRLA    BATTERIES; U.S. Ser. No. 10/046,659, filed Oct. 29, 2001, entitled    ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE; U.S. Ser. No.    09/993,468, filed Nov. 14, 2001, entitled KELVIN CONNECTOR FOR A    BATTERY POST; U.S. Ser. No. 09/992,350, filed Nov. 26, 2001,    entitled ELECTRONIC BATTERY TESTER, U.S. Ser. No. 60/341,902, filed    Dec. 19, 2001, entitled BATTERY TESTER MODULE; U.S. Ser. No.    10/042,451, filed Jan. 8, 2002, entitled BATTERY CHARGE CONTROL    DEVICE, U.S. Ser. No. 10/073,378, filed Feb. 8, 2002, entitled    METHOD AND APPARATUS USING A CIRCUIT MODEL TO EVALUATE CELL/BATTERY    PARAMETERS; U.S. Ser. No. 10/093,853, filed Mar. 7, 2002, entitled    ELECTRONIC BATTERY TESTER WITH NETWORK COMMUNICATION; U.S. Ser. No.    60/364,656, filed Mar. 14, 2002, entitled ELECTRONIC BATTERY TESTER    WITH LOW TEMPERATURE RATING DETERMINATION; U.S. Ser. No. 10/098,741,    filed Mar. 14, 2002, entitled METHOD AND APPARATUS FOR AUDITING A    BATTERY TEST; U.S. Ser. No. 10/101,543, filed Mar. 19, 2002,    entitled ELECTRONIC BATTERY TESTER; U.S. Ser. No. 10/112,114, filed    Mar. 28, 2002; U.S. Ser. No. 10/109,734, filed Mar. 28, 2002; U.S.    Ser. No. 10/112,105, filed Mar. 28, 2002, entitled CHARGE CONTROL    SYSTEM FOR A VEHICLE BATTERY; U.S. Ser. No. 10/112,998, filed Mar.    29, 2002, entitled BATTERY TESTER WITH BATTERY REPLACEMENT OUTPUT;    U.S. Ser. No. 10/119,297, filed Apr. 9, 2002, entitled METHOD AND    APPARATUS FOR TESTING CELLS AND BATTERIES EMBEDDED IN    SERIES/PARALLEL SYSTEMS; U.S. Ser. No. 10/128,790, filed Apr. 22,    2002, entitled METHOD OF DISTRIBUTING JUMP-START BOOSTER PACKS; U.S.    Ser. No. 60/379,281, filed May 8, 2002, entitled METHOD FOR    DETERMINING BATTERY STATE OF CHARGE; U.S. Ser. No. 10/143,307, filed    May 10, 2002, entitled ELECTRONIC BATTERY TESTER; U.S. Ser. No.    60/387,046, filed Jun. 7, 2002, entitled METHOD AND APPARATUS FOR    INCREASING THE LIFE OF A STORAGE BATTERY; U.S. Serial No.    10/177,635, filed Jun. 21, 2002, entitled BATTERY CHARGER WITH    BOOSTER PACK; U.S. Ser. No. 10/207,495, filed Jul. 29, 2002,    entitled KELVIN CLAMP FOR ELECTRICALLY COUPLING TO A BATTERY    CONTACT; U.S. Ser. No. 10/200,041, filed Jul. 19, 2002, entitled    AUTOMOTIVE VEHICLE ELECTRICAL SYSTEM DIAGNOSTIC DEVICE; U.S. Ser.    No. 10/217,913, filed Aug. 13, 2002, entitled, BATTERY TEST MODULE;    U.S. Ser. No. 60/408,542, filed Sep. 5, 2002, entitled BATTERY TEST    OUTPUTS ADJUSTED BASED UPON TEMPERATURE; U.S. Ser. No. 10/______,    (C382.12-0124), filed Sep. 18, 2002, entitled BATTERY TESTER UPGRADE    USING SOFTWARE KEY; U.S. Ser. No. 60/______, (C382.12-0137), filed    Oct. 2, 2002, entitled QUERY BASED ELECTRONIC BATTERY TESTER; and    U.S. Serial No. 10/______, (C382.12-0101), filed Oct. 2, 2002,    entitled ELECTRONIC BATTERY TESTER WITH RELATIVE TEST OUTPUT, which    are incorporated herein in their entirety.

SUMMARY OF THE INVENTION

An apparatus and method for monitoring a battery of an automotivevehicle are provided. An electrical connection to the battery orelectrical system of the vehicle. In various aspects, Kelvin connectionsare used for the electrical connection and may include voltage andcurrent sensors, either with or without the Kelvin connections. Aprocessor is used to determine a condition of the battery or ofcomponents of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram showing a battery monitor in avehicle in accordance with one embodiment of the present invention.

FIG. 2 is a more detailed schematic diagram showing the battery monitorof FIG. 1.

FIG. 3 is a simplified block diagram showing steps in performingdiagnostics in accordance with one aspect of the present invention.

FIG. 4 is a flow chart illustrating a boot sequence in accordance withone embodiment of the invention.

FIG. 5 is a flow charge illustrating a key off sequence of theinvention.

FIG. 6 is a flow chart illustrating a run mode in accordance with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention offers an apparatus and method for monitoring thecondition of the battery and optionally controlling charging of thebattery. Such a method and apparatus can be part of a general energymanagement system for a vehicle.

FIG. 1 is a simplified block diagram showing an automotive vehicle 10which includes a battery monitor 12 in accordance with one embodiment ofthe present invention. Vehicle 10 includes vehicle loads 14 which areshown schematically as an electrical resistance. A battery 18 is coupledto the vehicle load 14 and to an alternator 20. Alternator 20 couples toan engine of the vehicle 10 and is used to charge battery 18 and providepower to loads 14 during operation.

In general, automotive vehicles include electrical systems which can bepowered when the engine of the vehicle is operating by a generator, oralternator. However, when the engine is not running, a battery in thevehicle is typically used to power the system. Thus, the standardgenerator system in a vehicle serves two purposes. The generator is usedto supply power to the vehicle loads, such as lights, computers, radios,defrosters and other electrical accessories. Further, the generator isused to recharge the battery such that the battery can be used to startthe vehicle and such that the battery may power the electricalaccessories when the engine is not running.

One aspect of the invention includes the recognition that the conditionof a battery can be determined by making an initial assumption about aparameter of the battery, and modifying the assumed battery parameterbased upon certain measurements obtained from the battery duringcharging, discharging and/or idle periods. One specific aspect includesrecognizing two battery conditions that are significant to the operatorof a vehicle. The first condition is the ability of the battery tooperate (i.e., “crank”) the starter motor and the engine. The secondcondition is the ability of the battery to supply energy to electricalloads. For purposes of this aspect, indications of these conditions arecalculated as relative values referred to as the Cranking State ofHealth (CSOH) and the Reserve State of Health (RSOH), respectively. Thefollowing description sets forth example circuitry and measurementtechniques which can be used to obtain data for these determinations. Inone aspect, the particular techniques used to obtain the data are notrelevant to the invention and other techniques can be used.

In the embodiment illustrated in FIG. 1, battery monitor 12 includes amicroprocessor 22 coupled to a voltage sensor 24, a current sensor 26and a forcing function 28. Microprocessor 22 may also include one ormore inputs and outputs illustrated as I/O 30 adapted to couple to anexternal databus and/or to an internal databus associated with thevehicle 10. Further, a user input/output (I/O) 32 is provided forproviding interaction with a vehicle operator. In one embodiment,microprocessor 22 is coupled to alternator 20 to provide a controloutput 23 to alternator 20 in response to inputs, alone or in variousfunctional combinations, from current sensor 26, voltage sensor 24 andforcing function 28. In one embodiment, the control output 23 isconfigured to control alternator 20 such that a nominal voltage outputfrom alternator 20 is 12.6 volts, typical of the nominal open-circuitvoltage of the battery 18. Further, microprocessor 22 can raise theoutput voltage from alternator 20 in accordance with an inverserelationship to the state of charge of battery 18. This can beconfigured such that alternator 20 only charges battery 18 whennecessary, and only charges battery 18 as much as is necessary. Thischarging technique can increase battery life, lower componenttemperature of loads 14, increase the lifespan of loads 14 and savefuel. This configuration provides a feedback mechanism in which thestate of charge of battery 18 is used to control the charging of battery18. The battery monitor 12 is easily installed in a vehicle electricalsystem. A single shunt current sensor 26 can be inserted in one of theprimary battery cables and a control line provided to allow control ofalternator 20. The control can be by simply adjusting the voltagesupplied to a voltage regulator of alternator 20 to thereby controlcharging of battery 18. The battery monitor 12 can be a separate,self-sufficient and self-contained monitor which operates withoutrequiring interaction with other components of the vehicle, except insome embodiment, alternator 20.

FIG. 1 also illustrates a Kelvin connection formed by connections 36Aand 36B to battery 18. With such a Kelvin connection, two couplings areprovided to the positive and negative terminals of battery 18. Thisallows one of the electrical connections on each side of the battery tocarry large amounts of current while the other pair of connections canbe used to obtain accurate voltage readings. Because substantially nocurrent is flowing through the voltage sensor 24, there will be littlevoltage drop through the electrical connection between sensor 24 andbattery 18 thereby providing more accurate voltage measurements. Invarious embodiments, the forcing function 28 can be located physicallyproximate battery 18 or be connected directly to battery 18. In otherembodiments, the forcing function 28 is located anywhere within theelectrical system of vehicle 10. In one aspect, the present inventionincludes an in-vehicle battery monitor 12 which couples to battery 18through a Kelvin connection and further may optionally include a currentsensor 26 and may be capable of monitoring battery condition while theengine of vehicle 12 is operated, loads 14 are turned on and/oralternator 20 is providing a charge signal output to charge battery 18.In one particular embodiment, the combination of the Kelvin connectionformed by connections 36A and 36B along with a separate current sensor26 connected in series with the electrical system of the vehicle 10 isprovided and allows monitoring of the condition of battery 18 duringoperation of vehicle 10. The use of an current sensor 26 is used toprovide a monitor of the total current I_(T) flowing through battery 18.

In operation, microprocessor 22 is capable of measuring a dynamicparameter of battery 18. As used herein, a dynamic parameter includesany parameter of battery 18 which is measured as a function of a signalhaving an AC or transient component. Examples of dynamic parametersinclude dynamic resistance, conductance, admittance, impedance or theircombinations. In various aspects of the invention, this measurement canbe correlated, either alone or in combination with other measurements orinputs received by microprocessor 22, to the condition or status ofbattery 18. This correlation can be through testing of various batteriesand may be through the use of a lookup table or a functionalrelationship such as a characterization curve. The relationship can alsobe adjusted based upon battery construction, type, size or otherparameters of battery 18. Examples of various testing techniques aredescribed in the following references which are incorporated herein byreference U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin,entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 3,909,708,issued Sep. 30, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTINGDEVICE; U.S. Pat. No. 4,816,768, issued Mar. 28, 1989, to Champlin,entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,825,170,issued Apr. 25, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTINGDEVICE WITH AUTOMATIC VOLTAGE SCALING; U.S. Pat. No. 4,881,038, issuedNov. 14, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICEWITH AUTOMATIC VOLTAGE SCALING TO DETERMINE DYNAMIC CONDUCTANCE; U.S.Pat. No. 4,912,416, issued Mar. 27, 1990, to Champlin, entitledELECTRONIC BATTERY TESTING DEVICE WITH STATE-OF-CHARGE COMPENSATION;U.S. Pat. No. 5,140,269, issued Aug. 18, 1992, to Champlin, entitledELECTRONIC TESTER FOR ASSESSING BATTERY/CELL CAPACITY; U.S. Pat. No.5,343,380, issued Aug. 30, 1994, entitled METHOD AND APPARATUS FORSUPPRESSING TIME VARYING SIGNALS IN BATTERIES UNDERGOING CHARGING ORDISCHARGING; U.S. Pat. No. 5,572,136, issued Nov. 5, 1996, entitledELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOWSTATE-OF-CHARGE; U.S. Pat. No. 5,574,355, issued Nov. 12, 1996, entitledMETHOD AND APPARATUS FOR DETECTION AND CONTROL OF THERMAL RUNAWAY IN ABATTERY UNDER CHARGE; U.S. Pat. No. 5,585,728, issued Dec. 17, 1996,entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOWSTATE-OF-CHARGE; U.S. Pat. No. 5,592,093, issued Jan. 7, 1997, entitledELECTRONIC BATTERY TESTING DEVICE LOOSE TERMINAL CONNECTION DETECTIONVIA A COMPARISON CIRCUIT; U.S. Pat. No. 5,598,098, issued Jan. 28, 1997,entitled ELECTRONIC BATTERY TESTER WITH VERY HIGH NOISE IMMUNITY; U.S.Pat. No. 5,757,192, issued May 26, 1998, entitled METHOD AND APPARATUSFOR DETECTING A BAD CELL IN A STORAGE BATTERY; U.S. Pat. No. 5,821,756,issued Oct. 13, 1998, entitled ELECTRONIC BATTERY TESTER WITH TAILOREDCOMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,831,435, issuedNov. 3, 1998, entitled BATTERY TESTER FOR JIS STANDARD; U.S. Pat. No.5,914,605, issued Jun. 22, 1999, entitled ELECTRONIC BATTERY TESTER;U.S. Pat. No. 5,945,829, issued Aug. 31, 1999, entitled MIDPOINT BATTERYMONITORING; U.S. Pat. No. 6,002,238, issued Dec. 14, 1999, entitledMETHOD AND APPARATUS FOR MEASURING COMPLEX IMPEDANCE OF CELLS ANDBATTERIES; U.S. Pat. No. 6,037,777, issued Mar. 14, 2000, entitledMETHOD AND APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEXIMPEDANCE/ADMITTANCE; U.S. Pat. No. 6,051,976, issued Apr. 18, 2000,entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Pat. No.6,081,098, issued Jun. 27, 2000, entitled METHOD AND APPARATUS FORCHARGING A BATTERY; U.S. Pat. No. 6,091,245, issued Jul. 18, 2000,entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Pat. 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In the specific embodiment illustrated in FIG. 1, the forcing functionis a function which applies a signal having an AC (or having a timevarying or transient component) to battery 18. The forcing function canbe through the application of a load which provides a desired forcingfunction in which current is drawn from battery 18, or can be throughactive circuitry in which a current is injected into battery 18. Thisresults in a current labeled I_(F) in FIG. 1. The total current, I_(T)through battery 18 is due to both the forcing function current I_(F) andthe current flowing through loads 14, I_(L) Current sensor 26 ispositioned to sense the total current I_(L) One example battery dynamicparameter, the dynamic conductance (or reciprocally the batteryresistance) can be calculated as:ΔG=V=ΔI_(T)/ΔV  EQ. 1where ΔV is the change in voltage measured across the battery 18 byvoltage sensor 24 and ΔI_(T) is the change in total current measuredflowing through battery 18 using current sensor 26. Note that Equation 1uses current and voltage differences. In one embodiment, the change involtage and change in current are measured over a period of 12.5 secondsand at a rate of 50 msec to thereby provide a total of 20 readings forΔV and ΔI_(T) every second. The forcing function 28 is provided in orderto ensure that the current through battery 18 changes with time.However, in one embodiment, changes in I_(L) due to loads 14 or theoutput from alternator 20 can be used alone such that ΔI_(T)=ΔI_(L) andthe forcing function 28 is not required. In one aspect, the forcingfunction 28 is provided by normal or specially controlled operation ofloads 14.

In one embodiment, the voltage and current sensors provide synchronizedoperation, within one microsecond, and are substantially immune tomeasurement errors due to network propagation delays or signal lineinductance. Furthermore, microprocessor 22 can detect a failure of thevoltage regulator and alternator 20 if the voltage output exceeds ordrops below predetermined threshold levels. This information can beprovided to an operator through user interface 32, for example, a“service regulator soon” indication.

A temperature sensor 37 is provided which can be coupled directly to oneof the terminals of the battery 18 for measuring battery temperature.The temperature sensor 37 can be used in determining the condition ofthe battery, as battery condition is a function of temperature and canbe used in estimating the amount of power which will be required tostart the engine of the vehicle. Any type of temperature sensor can beused, for example, a thermistor, thermocouple, RTD, semiconductor orother temperature sensor. Another technique for measuring temperature isdescribed in U.S. Pat. No. 6,137,269, issued Oct. 24, 2000 and isincorporated herein by reference.

In one embodiment, current sensor 26 comprises a resistance shunt of 250μohms and current through the shunt is determined by measuring thevoltage drop across the shunt. However, other types of currentmeasurement techniques can also be used such as Hall Effect sensors orthrough an inductance probe. The change of voltage across the batteryand the resultant change in current through the battery is sampledusing, for example, one or more analog to digital converters. Thisinformation can be correlated to determine the total capacity, such asthe total Cold Cranking Amp (CCA) capacity of the battery.

Note that during the measurement cycle, vehicle loads 14 may be appliedunexpectedly causing noise to be present in the measurements. Onetechnique which might be considered to reduce the noise is to discardthose samples which are outside of a predetermined or adjustable windowor are outside of the dynamic range of the analog to digital converter.However, quite unexpectedly it has been found that the accuracy ofmeasurements can be increased by increasing the dynamic range of theanalog to digital converters, at the expense of the accuracy of thesamples obtained from the converter. By averaging all of the samples,even those which are statistically large or small relative to othersamples, the present invention is capable of providing accurate voltageand current measurements even in a noisy environment. By averagingsamples, and providing sufficient dynamic range for the analog todigital converter, no samples will be discarded and errors in themeasurements will tend to cancel against other errors.

In general, the present invention uses the direct relationship betweenthe dynamic conductance of the battery and the condition of the battery.For example, if a battery drops more than 15% below its rated capacity,microprocessor 22 can provide an output which indicates that the battery18 should be replaced. Further, the conductance can be used to determinethe charge level of the battery. Such a measurement can be augmented toimprove accuracy by monitoring the total current flowing into battery18, or out of battery 18, using current sensor 26. The voltage acrossthe battery 18 can also be used to determine the charge used in thedetermination of charge level. In general, the state of charge can bedetermined as a function of various combinations either alone ortogether of battery state of health, temperature, charge balance (chargegoing into and out of the battery), charging efficiency and initialconditions such as the battery construction, manufacture, plateconfiguration or other conditions of the battery. The functionalrelationship can be determined by characterizing multiple batteries,iterative techniques as described below, and/or through the use ofartificial intelligence techniques such as neural networks.

FIG. 2 is a more detailed schematic diagram of battery monitor 12. FIG.2 shows microprocessor 22 which includes a memory 40. FIG. 2 illustratesI/O 32 with which can be, for specific examples, a communication link inaccordance with various standards such as J1850, J1708, J1939, etc.Memory 40 is shown as an internal memory. However, external memory or anoptional external memory 42 can also be provided. In general, memory isprovided for storing programming functions, ratings, variables, etc.Microprocessor 22 can be a microcontroller or any type of digitalcircuitry and is not limited specifically to a microprocessor. FIG. 2illustrates forcing function 28 in greater detail and includes aresistance R₁ 44 and a switch S₁ 46 controlled by microprocessor 22.Switch 46 can be, for example, a field effect transistor. Voltage sensor24 is shown as including a differential amplifier 47 coupled to battery18 through a DC blocking capacitor C₁ 48. Shunt 26 is illustrated as aresistance R₂ 50 and a differential amplifier 52. Switches S₂ 54 and S₃56 are positioned to selectively couple amplifiers 52 and 47,respectively, to microprocessor 22 and are actuated by a sample controlline to provide data samples to microprocessor 22. An analog to digitalconverter can be an integral part of microprocessor 22 or it can be aseparate component to digitize the outputs from amplifiers 47 and 52.Capacitors C₂ and C₃ provide sample and hold circuits.

Forcing function 28 can be formed by a resistance as illustrated in FIG.2, or by a current sink or through an existing load of the vehicle.Switch S₁ 46 can be an FET, or biopolar transistor or can be amechanical or existing switch in the automotive vehicle. Although shunt26 is illustrated with a shunt resistance, other types of currentsensors such as Hall effect sensors or cable resistance based sensorscan be used. Other types of DC blocking techniques can be used toreplace capacitancy C₁ 48 such as a DC coupled amplifier.

FIG. 3 is a simplified block diagram 100 showing diagnostic stepsperformed by microprocessor 28 in accordance with the invention. Atblocks 102 and 104, the dynamic parameter(s) for the battery 18 areobtained and at block 104 data is collected. The type of data collectedat block 104 can be any type of data used in determining the conditionof the battery. For example, the data can be values used for ΔV andΔI_(T), information related to the type of battery, etc. Thisinformation can be stored in memory 40 for subsequent retrieval bymicroprocessor 22. The data can be collected over any time period andduring any type of engine or battery operation. At block 106,microprocessor 22 performs diagnostics or other computations based uponthe data stored in memory 40. If a battery fault or impending fault isdetected, an output can be provided at block 108 such as providing a“service battery soon” indication on the dash of the vehicle 10.

In one general aspect, the present invention determines the condition ofthe battery as a function of a stored battery parameter which is set toan initial value, modified based upon a measurement taken when theengine of the vehicle is not operating (or the battery is otherwise notbeing charged) and modified by a measurement taken when the engine ofthe vehicle is operating (or the battery is otherwise being charged).This can be an iterative process in which the modifications to thestored battery parameter continue as the vehicle is used. In onespecific example, a “Cranking State Of Health” (CSOH) can be determinedwhich is a relative indication of the ability of the battery to “crank”or actuate the starter motor of the vehicle. Another exampledetermination is “Reserve State Of Health” (RSOH) which is a relativeindication of the reserve capacity remaining in the battery. In anotherexample embodiment, a relative battery condition is determined basedupon a ratio between two quantities and as a function of a minimumthreshold value of a battery parameter, a measured battery parametervalue and a maximum observed value of a battery parameter value.

Turning now to a specific example embodiment of the present invention,the Cranking State Of Health (CSOH) can be calculated using Equation 2as follows:CSOH={[CCAcomp−CCAMIN]/[CCCA100SOC−CCAMIN]}×100  EQ. 2where CCAcomp is a compensated measured cold cranking amps of thebattery, CCAMIN is a minimum cold cranking amp value which is requiredby the engine and starter motors to crank and CCA100SOC is the coldcranking amps when the battery is at 100 percent state of charge and100% state of health (i.e., fully charged). CSOH is a ratio between twonumbers and will range between 0 and 100 percent. The present (i.e.,current), compensated CCA (CCAcomp) can be a function of averageobserved CCA over a time period, temperature and the current state ofcharge. This can initially be assumed to be a simple relationship, forexample, a straight line or simple curve. Actual values for therelationship can be learned. For example, the relationship to state ofcharge can be a ratio between CCA100SOC and a CCA value obtained whenthe state of charge is significantly less than 100 percent charged. Thiscan be through long term monitoring of the operation of the battery andengine in which the collected date is date and time stamped. Similarly,the relationship with temperature can initially be assumed but can belearned over time as a ratio CCAt1, CCAt2 where t1 and t2 aresubstantially different temperatures. Again, both quantities arepreferably captured at approximately equivalent times during operationof the battery of vehicle. For example, one value could be capturedduring nighttime periods where the engine is not running to obtain avery cold value and another value could be captured during daytime whilethe engine is running. In general, the formula for CCAcomp can beexpressed as:CCAcomp=CCAaverage·f(SOC)·f(T)  EQ. 3

Similarly, a relative indication of the reserve capacity of the battery,the Reserve State Of Health (RSOC) can be expressed:RSOH={[AHCapacity−AHMIN]/[AH100SOC−AHMIN]}×100  EQ. 4where AHCapacity is the present or current amp hour capacity of thebattery AHMIN is the minimum acceptable amp hour capacity of the batteryAH100SOC is the amp hour capacity of the battery at 100 percent state ofcharge (i.e., the battery is fully charged). RSOH ranges between 0 and100 percent. Amp hour capacity is given as: $\begin{matrix}{{AHCapacity} = \frac{\Delta\quad{Energy}}{\Delta\quad{SOC}}} & {{EQ}.\quad 5}\end{matrix}$

Equations 2 and 4 are functions of parameters which are not necessarilyinitially known of a battery. One aspect of the invention includes aniterative approximation technique which is used to arrive at suchparameters and which can be used in these or similar formulas. FIGS. 4,5 and 6 are simplified block diagrams which illustrate one exampletechnique for such estimations. Using Equation 2 as an example,CCA100SOC is initially assumed to be CCAMIN. CCAMIN can be programmedinto a memory in the vehicle (such as memory 40 shown in FIG. 2) duringmanufacture or otherwise stored and is the minimum acceptable CCA of thebattery. As the vehicle is operated, and the battery is charged anddischarged, the state of charge can be monitored and a maximum observed.The CCA measurement wherein the state of charge is 100% is stored inmemory and is assigned to CCA100SOC.

Turning to FIG. 4, a flow chart 100 is shown that illustrates a “boot”procedure 100. This boot procedure 100 is typically initiated any timethe memory 40 has been erased or if microprocessor 22 detects that thebattery 18 has been disconnected. The procedure 100 starts at startblock 102. At block 104 values for CCAMIN and AHMIN are retrieved frommemory within the vehicle for memory (such as memory 4). For example,this information can be permanently stored in a memory duringmanufacture of the vehicle or otherwise programmed. Note that thevarious instructions are used to implement these steps normally bestored in a memory such as memory 40 and carried out by microprocessor22.

At block 106, values for CCA and amp hour capacity at 100 percent stateof charge (CCA100SOC and AH100SOC) are said equal to CCAMIN and AHMIN,respectively. Note that this is an assumption, however, it provides astarting point for the observation process. At block 108, the state ofcharge is assumed to be a function of voltage. One simple function is asto relate the state of charge to the open circuit voltage:SOC=1250·Voc−1475  EQ. 6

At block 110, flags are cleared to indicate that the values have been“learned”. At block 114, control is passed to another appropriate blocksuch as those shown in FIGS. 5 and 6.

FIG. 5 is a simplified block diagram of a key off procedure 120. Key offprocedure 120, as the name implies, occurs during periods when theengine of the vehicle is not running or the battery is not otherwisebeing charged. The procedure begins at block 122. At block 124, variousdata is obtained from the battery such as voltage, current andtemperature. Block 126 causes the procedure to wait until the batteryhas reached an equilibrium. For example, it can be assumed that thebattery is at equilibrium if the temperature and the voltage aresubstantially constant. Once the battery has reached equilibrium, thestate of charge of the battery is determined as a function, temperatureand open circuit voltage at block 128. For example, one such state ofcharge formula is as follows:SOC=1250Voc _(∝)−1475+V _(TC)  EQ. 7

At block 130, if the state of charge is determined to be 100 percent,control is passed to block 132. One technique for determining if thestate of charge is at 100 percent is by observing a reduction in theamount of charge current which the battery is accepting.

At block 132, a new open circuit voltage flag is set. The flag is usedto alert the program that a stable condition has been met. Additionally,at block 130, if the state of charge does not equal 100 percent, controlis passed to block 134. At block 134, if the state of charge is notgreater than x control is passed to block 124. X is a setable percentagewhich is typically selected to be between %5 and 10%. Alternatively,control is passed to block 136. At block 136, the amp hour capacity ofthe battery is calculated as a function of the change in energy suppliedto or drawn from the battery, the temperature and the current. Oneexample formula is: $\begin{matrix}{{AHCapacity} = {\frac{\Delta\quad{Energy}}{\Delta\quad{SOC}}.}} & {{EQ}.\quad 8}\end{matrix}$

FIG. 6 is a block diagram 160 showing operation while the engine isrunning or the battery 18 is being charged. Flow chart 160 begins atblock (where energy=AH*f(T)*f(SOC)) 162 and control is passed to block164. At block 164, a variable LASTSOC is set to the current state ofcharge. At block 166, data is collected such as voltage, current,temperature and conductance. At block 168, the current state of chargeis determined as the last state of charge plus a quantity which is afunction of the change in energy, the temperature and the current intoor out of the battery. Equation 9 can be used as follows:$\begin{matrix}{{SOC} = {{LASTSOC} + \frac{\Delta\quad{Energy}}{AHCapacity}}} & {{EQ}.\quad 9}\end{matrix}$

At block 170, if the state of charge is less than 0, then the state ofcharge is forced to equal 0. On the other hand, at block 172, if thestate of charge is greater than 100 the state of charge is forced to avalue of 100. At block 174, if the compensated CCA reading is greaterthan CCA100SOC, then CCA100SOC is set equal to CCAcomp. At block, 176, anew CCA flag is set which is used to indicate a new CCA value has beenobtained and control is returned to block 164. This procedure repeatsuntil the engine is turned off, the battery is disconnect or thecharging cycle is otherwise interrupted.

As the data is collected, the formulas set forth above are used tocalculate the RSOH and the CSOH. This information can be provided in anyappropriate form to an operator. For example, a normal display can beprovided or a graphical form can be used. An empty/full gauge can beused to provide an output which is familiar to most drivers. A “servicebattery soon” indication is another example output. The values can alsobe used to control operation of the alternator 10 or stored for futureretrieval by diagnostic equipment or to validate warranty claims.

In another aspect, a state of life (SOL) of the battery 18 is determinedby microprocessor 22. The state of life provides an indication of whatthe current age of a battery is and can be related to the life span ofthe battery. For example, SOL can be an indication of present batteryage relative to the total lifespan of the battery. For example, thestate of life can indicate that the battery life is a certain percentspent, that a battery is a number of years old or that a battery has acertain number of years remaining in its life. Only one specificexample, the reserved state of life is a function of the reserved stateof health (RSOH) from equation 4 and the cranking state of health (CSOH)from equation 2. A specific relationship is as follows:SOL=RSOH·CSOH  Equation 10

Various calibration factors in/or offsets or other functions can be usedto manipulate Equation 10 to relate the state of life to the desiredunit. The microprocessor 22, so determines if the battery 18 has beenreplaced with a different battery. For example, microprocessor 22 canstore historical information such as past measurements of a dynamicparameter of the battery 18. The past measurement can be from theprevious time the vehicle was operated, from a parameter measured withinthe past month or longer, or from multiple parameters which werepreviously measured. A current or more recent measurement is thencompared with the past measurement. If the percentage change is morethan a predetermined amount, for example 10%, the microprocessor 22makes a determination that a new battery 18 has been placed into thevehicle. Upon such a determination, the microprocessor can begin thelearning process discussed above and updates a stored parameter of thebattery.

A constant offset value can be introduced prior to digitization of thecurrent sampled by the current sensor 26. For example, referring to FIG.2, a voltage offset can be introduced prior to the sensed current signalfrom sensor 26 being digitized by processor 22. This reduces the dynamicrange required by the microprocessor to obtain an accurate measurementfor calculating a dynamic parameter. Further, processor 22 can enter asleep mode during periods of vehicle inactivity and can be reactivatedfrom the sleep mode if the sensed current is at least greater than theconstant offset. To various different constant offsets can be used asdesired. For example, one constant offset value can be used duringvehicle operation in and a second constant offset value can be usedduring vehicle inactivity. If the A to D conversion yields a resultwhich is approximately 0, the processor can use the value of theconstant offset and assume that it represents the actual current. Whencurrent values are integrated over time, errors due to noise or othersources are reduced.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, the circuitry, circuitconfiguration, and battery condition parameters are provided as simplyexample embodiments and those skilled in the art will recognize thatother configurations and implementations can be used. The particularconnections to the battery can be through Kelvin connections whichinclude a “split” Kelvin connection in which the forcing functionconnection(s) are/is spaced apart from the battery such as thatdescribed and illustrated in U.S. patent application Ser. No.09/431,697, filed Nov. 1, 1999 and entitled ELECTRICAL CONNECTION FORELECTRONIC BATTERY TESTER, now U.S. Pat. No. 6,163,156 which isincorporated herein by reference in its entirety. In a further exampleof the present invention, alternator 20 can comprise an electronicbattery charger such as those used to charge automotive vehicles whenthe vehicle is stationary or to charge stand by batteries such as thoseused in remote systems such as cellular sites. In such an embodiment,control line 23 is used to adjust the charger of battery 18 using thetechniques set forth herein. In such an embodiment, element 10 shown inFIG. 1 illustrates a standby power supply for equipment.

1-17. (canceled).
 18. A battery monitor for use in monitoring a batteryof an automotive vehicle comprising: a voltage sensor configured tomonitor a voltage across the battery; a current sensor configured tomonitor an electrical current through the battery; a processorconfigured to measure a parameter of the battery with the current sensorand the voltage sensor, compare the measured parameter with a historicalparameter and identify replacement of the battery based upon thecomparison.
 19. The apparatus of claim 18 wherein the replacement of thebattery is identified if the measured parameter is within 10% of thehistorical parameter.
 20. The apparatus of claim 18 wherein thehistorical parameter is less then one month old.
 21. The apparatus ofclaim 18 wherein the historical parameter is from a previous time thevehicle was operated.
 22. The apparatus of claim 18 wherein in responseto replacement of the battery the processor updates a stored parameterof the battery.
 23. The apparatus of claim 18 wherein the microprocessordetermines condition of the battery as a function of the storedparameter of the battery.
 24. The apparatus of claim 18 wherein theparameter comprises a dynamic parameter.
 25. The apparatus of claim 18,including: a voltage sensor configured to monitor a voltage across thebattery; a current sensor configured to monitor an electrical currentthrough the battery; an analog to digital converter configured toconvert sensed current from the current sensor to a digital value; and aconstant offset configured to reduce a quiescent current draw from thesensed current prior to digitizing the sensed current by the analog todigital converter.
 26. The apparatus of claim 25 wherein the processorenters a sleep mode during periods of vehicle inactivity and isactivated from the sleep mode if current is greater than at least theconstant offset.
 27. The apparatus of claim 25 wherein the constantoffset has a first value during vehicle operation and a record valueduring vehicle inactivity.
 28. The apparatus of claim 25 wherein theprocessor integrates digitized current values over time.
 29. Theapparatus of claim 25 the processor uses the constant offset forcalculations of the digitized current is less than a threshold.
 30. Theapparatus of claim 18, including: a communication link configured tocouple to a data bus of the vehicle; and wherein the processor isfurther configured to receive a signal from the data bus indicative ofoperation of an electrical component of the vehicle and responsivelywake up from a sleep mode to monitor the electrical current through thebattery using the current sensor.
 31. The apparatus of claim 30 whereinthe processor re-enters the sleep mode after operation of the electricalcomponent has terminated.
 32. The apparatus of claim 30 wherein thesignal indicates a door of the vehicle has opened.
 33. A battery monitorfor monitoring a battery of an automotive vehicle, comprising: a voltagesensor configured to monitor a voltage across the battery; a currentsensor configured to monitor an electrical current through the battery;an analog to digital converter configured to convert sensed current fromthe current sensor to a digital value; a constant offset configured toreduce a quiescent current draw from the sensed current prior todigitizing the sensed current by the analog to digital converter; and aprocessor configured to measure a parameter of the battery as a functionof sensed current and sensed voltage.
 34. The apparatus of claim 33wherein the processor enters a sleep mode during periods of vehicleinactivity and is activated from the sleep mode if current is greaterthan at least the constant offset.
 35. The apparatus of claim 33 whereinthe constant offset has a first value during vehicle operation and arecord value during vehicle inactivity.
 36. The apparatus of claim 33wherein the processor integrates digitized current values over time. 37.The apparatus of claim 33 the processor uses the constant offset forcalculations of the digitized current is less than a threshold.
 38. Theapparatus of claim 33, including: a communication link configured tocouple to a data bus of the vehicle; and wherein the processor isfurther configured to receive a signal from the data bus indicative ofoperation of an electrical component of the vehicle and responsivelywake up from a sleep mode to monitor the electrical current through thebattery using the current sensor.
 39. The apparatus of claim 38 whereinthe processor re-enters the sleep mode after operation of the electricalcomponent has terminated.
 40. A battery monitor for monitoring a batteryof an automotive vehicle, comprising: a current sensor configured tomonitor an electrical current through the battery; a communication linkconfigured to couple to a data bus of the vehicle; and a processorconfigured to receive a signal from the data bus indicative of operationof an electrical component of the vehicle and responsively wake up froma sleep mode to monitor the electrical current through the battery usingthe current sensor.
 41. The apparatus of claim 40 wherein the processorre-enters the sleep mode after operation of the electrical component hasterminated.
 42. The apparatus of claim 40 wherein the signal indicates adoor of the vehicle has opened.